Immunomodulatory activity of a lupane triterpenoid ester isolated from the eastern Nigeria mistletoe,Loranthus micranthus(Linn)

<正>Objective:To provide further evidence for the ethnomedicinal use of the Eastern Nigeria mistletoe,Loranthus micranthus(L.micranthus),as an immunostimulant.Methods:Solvent fractions from the crude extract of the mistletoe plant was obtained and screened by the cell mediated delayed type hypersensitivity reaction(DTHR) model in mice.Then the immunomodulatory potentials of a major lupane triterpenoid ester isolated from an active hexane fraction of the Eastern Nigeria mistletoe was investigated.Three lupeol-based triterpenoid esters: 7β15α-dihydroxyl-lup-20(29)-ene-3β-palmitate(Ⅰ),7β,15α-dihydroxyl-lup-20(29)- ene-3β-stearate(Ⅱ) and 7β,15α-dihydroxyl-lup-20(29)-ene-3β-decadecanoate(Ⅲ) were isolated from the plant leaves epiphyting on a local kola nut tree and were characterized. Compound 1 was subjected to cell proliferation studies using C57H1/6 splenocvtes at three dose levels(5.25 and 100μg/mL) in presence of controls.Furthermore,the effect of this compound on IL-8 receptor expression was evaluated at three doses(1,5 and 10μg/mL) using the real time polymerase chain reaction assay.Results:This triterpenoid ester produced some enhancement of the splenocytes at the tested doses but at doses higher than 5μg/mL caused inhibition of the IL-8 receptor expression.Conclusions:The present findings support the ethnomedicinal use of the Eastern Nigeria Mistletoe in the management of diseases affecting the immune system.The trilerpenoid(s) have some immunomodulatory abilities on splenocytes and IL-8 receptors and may partly account lor the overall immunomodulatory activity of this plant.